1. Field of the Invention
This invention relates to articles of manufacture comprising ionomeric ethylene copolymers blended with organic acids or salts of organic acids. The polymer blends are characterized by a unique combination of high resilience and stiffness. Articles of manufacture in which such properties are desirable include, without limitation, footwear structural components, golf club components, and industrial materials.
2. Description of Related Art
Several patents and publications are cited in this description in order to more fully describe the state of the art to which this invention pertains. The entire disclosure of each of these patents and publications is incorporated by reference herein.
Many articles of manufacture would benefit from a balance of properties including high resilience and stiffness. For example, footwear structural components such as heel counters, toe puffs, shanks, and soles provide shape support for footwear construction. A wide range of materials has been used to prepare these footwear components, including metal, leather, cardboard, laminated materials, foams, thermoplastic resins, and the like.
For the structural components of certain types of footwear, it would be useful to develop a material having a combination of stiffness and resilience, to provide improved shape support and crush resistance. Other desirable properties for footwear structural components include low density, low cost, adhesion to fabrics, and processing versatility, including improved heat stability and melt processibility. It is also desirable for such materials to be recyclable for economy and environmental compatibility.
As a result of their resilience, stiffness, toughness and durability, and because they are recyclable, various ionomeric resins sold by E. I. du Pont de Nemours and Company under the trademark Surlyn® and by the Exxon Corporation under the tradenames Escor™ and Iotek™ have become materials of choice for a number of applications, including the construction of certain footwear components.
In addition, some ionomer blends are known for use in footwear structural components. For example, JP10120842 describes an ionomeric composition comprising: (a) a partially neutralized ethylene acid copolymer having 5 to 30 wt % unsaturated carboxylic acid, melt flow rate of 0.1 to 100 g/10 min, and flexural modulus greater than 150 mPa; (b) a partially neutralized ethylene acid copolymer having 20 to 50 wt % unsaturated carboxylic acid, melt flow rate of 20 to 1000 g/10 min, and (c) reinforcing fiber.
JP3034614 describes an ionomeric composition comprising a blend of an ethylene acid copolymer neutralized from 10 to 80% and a polyester acid copolymer.
JP09108007 describes an ionomeric composition comprising an ethylene acid copolymer containing 17 to 30 wt % of (meth)acrylic acid neutralized from 5 to 40%.
Although certain conventional ionomers and blends, as described above, have proven suitable for use in footwear structural components, it would be useful to develop a material having a combination of higher stiffness and greater resilience than conventional ionomers. Such a material would provide improved shape support and crush resistance for footwear structural components and other applications.
It is particularly desirable to develop compositions of ethylene/acid copolymers with low to medium acid content that exhibit stiffness and resilience comparable to or exceeding that exhibited by conventional high acid ionomers. Such materials have use in many articles of manufacture, including, without limitation, footwear structural components, golf club components, and also in a wide variety of industrial materials, such as caulking materials, sealants, modifiers for cement and asphalt, coatings, packaging films, molded parts, and resilient foams for sporting goods.